Yongwen Ma

The fate of di-n-butyl phthalate in a laboratory-scale anaerobic/anoxic/oxic wastewater treatment process.

A laboratory-scale anaerobic/anoxic/oxic (AAO) wastewater treatment system was employed to investigate the effects of hydraulic retention time (HRT) and sludge retention time (SRT) on the removal and fate of di-n-butyl phthalate (DnBP). HRT had no significant effect on DNBP removal between 12 and 30 h. However, longer HRT increased DnBP accumulation in the system and DnBP retention in the waste sludge. When SRT was increased from 15 to 25 d, DnBP removal efficiency stayed above 95%. Compared to the removal of only 90% at SRT of 10d, longer SRT enhanced DnBP degradation efficiency. The optimal HRT and SRT for both nutrients and DnBP removal were 18 h and 15 d. At these retention times, about 72.66% of DnBP was degraded by the activated sludge process, 2.44% was released in the effluent, 24.44% was accumulated in the system, and 0.5% remained in the waste sludge. The anaerobic, anoxic and oxic reactors were responsible for 17.14%, 15.02% and 63.46% of the overall DnBP removal, respectively. Meanwhile a removal degradation model was formulated, and kinetic parameters were evaluated with batch experiments under anaerobic, anoxic, oxic conditions. The model can well forecast the effluent quality of anaerobic/anoxic/oxic reactors of the AAO process.

Fe/S doped granular activated carbon as a highly active heterogeneous persulfate catalyst toward the degradation of Orange G and diethyl phthalate.

Fe/S doped granular activated carbon (Fe/SGAC) was synthesized with ferric nitrate, Na2S2O3 and (NH4)2S2O8 via an impregnation-precipitation, reduction-oxidation combining with aqueous-phase synthesis method treatment. Surface density of functional groups, surface area changes as well as the chemical state inside Fe/SGAC catalyst were studied by Boehm titration, N2 adsorption and X-ray photoelectron spectroscopy (XPS). The reactivity of the catalysts was tested by degrading Orange G (OG) and diethyl phthalate (DEP). The Fe/SGAC catalysts could significantly enhance the removal rate of OG as compared to persulfate alone and PS/GAC. And the catalytic capacity was also enhanced by S doping. But the degradation of DEP under the similar condition was inhibited by adsorption process because of the different hydrophobicities of OG and DEP molecule. Fe2O3/FeOOH (Fe(3+)) (represents ferrihydrite) together with FeO/Fe3O4 (Fe(2+)) and Fe2O3-satellite, which provide the new active site for persulfate catalyst was found to be the major components of iron element in Fe/SGAC catalyst; the existence of FeS2(S(-)) for sulfur element verified the assumption that the doped S element promoted the electron transfer between the persulfate species and iron oxide at the interface. COD removal experiment further confirmed that mostly contaminant removal was owed to the Fe/SGAC catalytic persulfate oxidation process.

A fast predicting neural fuzzy model for on-line estimation of nutrient dynamics in an anoxic/oxic process.

In this paper a software sensor based on a fuzzy neural network approach was proposed for real-time estimation of nutrient concentrations. In order to improve the network performance, fuzzy subtractive clustering was used to identify model architecture, extract and optimize fuzzy rule of the model. A split network structure was applied separately for anaerobic and aerobic conditions was employed with dynamic modeling methods such as autoregressive with exogenous inputs and multi-way principal component analysis (MPCA). The proposed methodology was applied to a bench-scale anoxic/oxic process for biological nitrogen removal. The simulative results indicate that the learning ability and generalization of the model performed well and also worked well for normal batch operations corresponding to three data points inside the confidence limit determined by MPCA. Real-time estimation of NO(3)(-), NH(4)(+) and PO(4)(3-) concentration based on fuzzy neural network analysis were successfully carried out with the simple on-line information regarding the anoxic/oxic system.

Stormwater runoff pollutant loading distributions and their correlation with rainfall and catchment characteristics in a rapidly industrialized city.

Fast urbanization and industrialization in developing countries result in significant stormwater runoff pollution, due to drastic changes in land-use, from rural to urban. A three-year study on the stormwater runoff pollutant loading distributions of industrial, parking lot and mixed commercial and residential catchments was conducted in the Tongsha reservoir watershed of Dongguan city, a typical, rapidly industrialized urban area in China. This study presents the changes in concentration during rainfall events, event mean concentrations (EMCs) and event pollution loads per unit area (EPLs). The first flush criterion, namely the mass first flush ratio (MFFn), was used to identify the first flush effects. The impacts of rainfall and catchment characterization on EMCs and pollutant loads percentage transported by the first 40% of runoff volume (FF40) were evaluated. The results indicated that the pollutant wash-off process of runoff during the rainfall events has significant temporal and spatial variations. The mean rainfall intensity (I), the impervious rate (IMR) and max 5-min intensity (Imax5) are the critical parameters of EMCs, while Imax5, antecedent dry days (ADD) and rainfall depth (RD) are the critical parameters of FF40. Intercepting the first 40% of runoff volume can remove 55% of TSS load, 53% of COD load, 58% of TN load, and 61% of TP load, respectively, according to all the storm events. These results may be helpful in mitigating stormwater runoff pollution for many other urban areas in developing countries.

Degradation of refractory dibutyl phthalate by peroxymonosulfate activated with novel catalysts cobalt metal-organic frameworks: Mechanism, performance, and stability.

In this work, a new effective and relatively stable heterogeneous catalyst of Metal-Organic Framework Co3(BTC)2·12H2O (Co-BTC) has been synthesized and tested to activate peroxymonosulfate (PMS) for removal of refractory dibutyl phthalate (DBP). Co-BTC(A) and Co-BTC(B) were synthesized by different methods, which resulted in different activity towards PMS. The results indicated that Co-BTC(A) showed better performance on DBP degradation. The highest degradation rate of 100% was obtained within 30min. The initial pH showed respective level on DBP degradation with a rank of 5.0>2.75>9.0>7.0>11.0 in PMS/Co-BTC(A) system. No remarkable reduction of DBP was observed in the catalytic activity of Co-BTC(A) at 2nd run as demonstrated by recycling. However, the DBP degradation efficiency decreased by 8.26%, 10.9% and 25.6% in the 3rd, 4th, and 5th runs, respectively. The loss of active catalytic sites of Co(II) from Co-BTC(A) is responsible for the activity decay. Sulfate radicals (SO4(-)) and hydroxyl radicals (OH) were found at pH 2.75. Here, we propose the possible mechanism for activation of PMS by Co-BTC(A), which is involved in homogeneous and heterogeneous reactions in the solutions and the surface of Co-BTC(A), respectively.

A hybrid genetic--neural algorithm for modeling the biodegradation process of DnBP in AAO system.

A hybrid artificial neural network - genetic algorithm numerical technique was successfully developed to model, and to simulate the biodegradation process of di-n-butyl phthalate in an anaerobic/anoxic/oxic (AAO) system. The fate of DnBP was investigated, and a removal kinetic model including sorption and biodegradation was formulated. To correlate the experimental data with available models or some modified empirical equations, the steady state model equations describing the biodegradation process have been solved using genetic algorithm (GA) and artificial neural network (ANN) from the water quality characteristic parameters. Compared with the kinetic model, the performance of the GA-ANN for modeling the DnBP was found to be more impressive. The results show that the predicted values well fit measured concentrations, which was also supported by the relatively low RMSE (0.2724), MAPE (3.6137) and MSE (0.0742)and very high R (0.9859) values, and which illustrates the GA-ANN model predicting effluent DnBP more accurately than the mechanism model forecasting.

Activation performance and mechanism of a novel heterogeneous persulfate catalyst: metal–organic framework MIL-53(Fe) with FeII/FeIII mixed-valence coordinatively unsaturated iron center

In this work, a novel effective heterogeneous catalyst metal-organic framework MIL-53(Fe) has been synthesized for the purpose of activating persulfate (PS). Catalytic performance of MIL-53(Fe) activated under different vacuum conditions was investigated; stability and reusability of the catalyst were evaluated, and the activation mechanism was also investigated. The results indicated that vacuum activation could cause variation of the FeII/FeIII relative amount ratio of the catalyst, and thus would change the catalytic activities of MIL-53(Fe), because FeII or FeIII CUS (coordinative unsaturated metal site) are alternative active sites. It was found that MIL-53(Fe)-2 exhibits good performance for PS activation and could be used for multiple cycles. A removal rate of 98% for Orange G was obtained within 120min (95.7% mineralization efficiency), and 94.3% was attained in the fifth cycle. The mechanism of the activation of PS by MIL-53(Fe) was also suggested, which involves a predominant heterogeneous reaction and an auxiliary homogeneous reaction. The findings of this study provide new insight into the application of the reactive metal-organic frameworks in activating persulfate for the degradation of environmental contaminants.

Modification of properties of old newspaper pulp with biological method.

Modification of properties of old newspaper (ONP) deinked pulp with laccase and histidine was investigated. It was found that the optimum conditions for laccase-histidine treatment were: the concentration of laccase 0.9 U/g dry pulp, the concentration of histidine 1% relative to the dry pulp, room temperature, reaction time 1.5h, pH 7, the pulp consistency 5% and O(2) atmosphere. The results also showed that, in the optimum conditions, compared to the control pulp, the wet tensile strength, the carboxyl group content and water retention value of ONP treated with laccase and histidine were increased by 55.1%, 39.1% and 45.7%, respectively. Moreover, environmental scanning microscope images showed that more collapse and more fibrillation were observed on the laccase-histidine-treated fiber surface than the control samples, which led to form better bonding between fibers in handsheets resulting in the increase of the paper strength of laccase-histidine-treated ONP pulp.

Modification of old corrugated container pulp with laccase and laccase-mediator system.

Modification of the physical properties of old corrugated container (OCC) pulp with laccase or a laccase-mediator (ABTS, HBT, VA) system was investigated under select enzymatic concentrations and reaction times. The optimal conditions for laccase treatment shown to be using a laccase dose of 160U/g o.d. pulp, a treatment time of 20h at 25°C, pH 7 with a pulp consistency of 5%. Results showed that the Lac-HBT treated OCC pulp gave the best strength properties, improving tensile strength by 15.7%. The increase in the carboxyl group content of OCC laccase or Lac-HBT treated pulp led to the increase in the swelling ability and bonding between fibers. Microscope images showed the fiber surface became rougher and more collapsible after Lac-HBT treatment. FT-IR data showed that new carboxylic acid groups were formed during Lac-HBT treatment.

Different Co-based MOFs templated synthesis of Co3O4 nanoparticles to degrade RhB by activation of oxone

In this study, Co-based MOF with a 2D structure, 3D microrod structure and 3D nano-dodecahedral structure was synthesized by the coordination of cobalt ions and different organic ligands. Then, Co3O4, which was derived from these Co-based MOFs, was used to activate oxone for RhB degradation. It was found that the morphology and structure of the templates can significantly influence the formation of the nano Co3O4 products, which has an indirect effect on the catalytic ability of the resulting Co3O4 for oxone to degrade RhB. Among the products, nano-sphere Co3O4, which was derived from a template with a 3D nano-dodecahedral structure (ZIF-67) can effectively activate oxone to degrade RhB. Under neutral conditions, the rate constant of the degradation of RhB (0.1 mM) was 0.0509 min−1 with 50 mg L−1 catalyst and 1.0 mM oxone based on first-order kinetics. In addition, the influence of a series of parameter factors (pH, the dosage of catalyst and oxone) on the catalyst was also studied. Low cobalt ion dissolution (0.04 mg L−1 at pH = 3, <0.01 mg L−1 at pH = 7) and good recyclability (degradation rate of RhB after 5 cycles: close to 96%, 89% at pH = 7, pH = 3) further proved that the as-prepared Co3O4 can be used as a promising catalyst.